This invention is in great part an extension of U.S. Pat. No. 4,138,686 to show in more detail how the printing method claimed therein can be applied in specific configurations for best results. The method of droplet selection and in some cases the method of dispersal, perpendicular to the motion of the output, of successive impact points of droplets from a particular stream, have been previously described. However, a more detailed discussion of droplet impact sequencing schemes (rastering) and implementation methods therefor would be useful.
Further, since successive droplets from a particular stream impact the output at slightly different times during a scan interval, a correction must be made for motion of the output means relative to the selector means, so that all droplets in a scan will impact the output at points along a line on the output surface and perpendicular to its direction of motion. Further for best output results corrections must be made for predictable unequal droplet travel times, due to a preceding droplet being unselected for impact and thus disrupting air flow along the droplet stream.
Also a new means to continually synchronize droplet arrival times at selector sites with site activation times in case droplet speeds drift during operation will be discussed in detail for various versions of the contact electrostatic selectors, such as those described in U.S. Pat. No. 4,138,686.